Up to now, redox (oxidation-reduction) capacitors are popular. One example of such redox capacitors includes an electrode sheet, which is made by supporting an oxide such as manganese on a surface of activated carbon, mixing the activated carbon with conductive carbon or the like, and applying or rolling the mixed carbon onto a power collecting metal. Further, Patent Citation 1 discloses a capacitor in which electrodes are made of porous conductive ceramics prepared by the sol-gel process. Still further, Patent Citation 2 proposes a capacitor electrode which is made by uniformly forming a thin metal oxide film on acetylene black, and applying the thin oxide film onto a power collecting metal which has been mixed with carbon powder or the like.
The capacitor electrode of Patent Citation 1 has minute holes in the unit of nano and a large surface area. However, the conductive oxide of the capacitor electrode has a micromesh structure, so that the capacitor electrode suffers from high internal resistance and insufficient response. If a substrate for strengthening the capacitor electrode has poor conductivity, the capacitor electrode suffers from further increased internal resistance. With Patent Citation 2, the capacitor electrode has a large surface area, but becomes less effective as a whole since the carbon or the like has to be added. In addition, the power collector has to be used. Patent Citation 3 proposes a capacitor electrode which includes amorphous tungsten oxide, and has a large capacity. However, conductivity of a whisker itself is low compared with that of crystal tungsten oxides. Further, cyclic decay resistance of the whisker is low compared with that of the crystal tungsten oxide.
This invention has been contemplated in order to overcome problems of the related art, and is intended to provide a capacitor electrode which has low internal resistance and excellent conductivity, and a method of manufacturing such a capacitor electrode.    Patent Citation 1: Patent Laid-open Publication No. 2002-299164    Patent Citation 2: Patent Laid-open Publication No. 2004-103669    Patent Citation 3: Patent Laid-open Publication No. 2005-252217